Refrigeration equipment

ABSTRACT

A refrigeration equipment includes a vapor compression type of refrigerant circuit that prevents a decline in refrigeration ability in user side heat exchangers when the refrigerant condensed by a heat source side heat exchanger is reduced in pressure and sent to the user side heat exchangers. An air conditioner includes a refrigerant liquid junction line and a refrigeration gas junction line, a heat source side expansion valve, a cooler, and a first pressure detection mechanism. The heat source side expansion valve reduces the pressure of the refrigerant that is condensed in the heat source side heat exchanger and sent to the user side heat exchangers. The cooler cools the refrigerant that is condensed in the heat source side heat exchanger and sent to the user side heat exchangers. The first pressure detection mechanism detects the pressure of the refrigerant after the pressure thereof has been reduced by the heat source side expansion valve.

TECHNICAL FIELD

The present invention relates to a refrigeration equipment, and moreparticularly to a refrigeration equipment having a vapor compressiontype of refrigerant circuit.

BACKGROUND ART

One example of a conventional refrigeration equipment that includes avapor compression refrigeration circuit is an air conditioner that isemployed to provide air conditioning for buildings or the like. Thistype of air conditioner primarily includes a heat source unit, aplurality of user units, and a refrigerant gas junction line and arefrigerant liquid junction line that serve to connect these unitstogether. The refrigerant gas junction line and the refrigerant liquidjunction line of the air conditioner are positioned so as to connect theheat source unit and the plurality of user units, and thus the lines arelong and have a complex line shape that includes many curves andbranches along the length thereof. Because of this, when the airconditioner is to be renovated, there will be many occasions in whichonly the heat source unit and the user units are renovated, and therefrigerant gas junction line and the refrigerant liquid junction lineof the preexisting device are left in place.

In addition, many conventional air conditioners use an HCFC refrigerantsuch as R22. The lines, devices, and the like that form the refrigerantcircuit of this type of air conditioner have a strength that correspondsto the saturation pressure of the operating refrigerant at a normaltemperature. However, because environmental problems are being takeninto consideration in recent years, there are continuing efforts beingmade to replace HCFC refrigerants with HFC or HC refrigerants. Becauseof this, air conditioners that are employed to air condition buildingsor the like are being renovated by replacing the preexisting heat sourceunit and the user units that use R22 as the operating refrigerant withdevices that use HFC refrigerants such as R407C that approximate thesaturation pressure characteristics of R22 as the operating refrigerant,and reusing the refrigerant gas junction line and the refrigerant liquidjunction line of the preexisting air conditioner.

On the other hand, it is desirable for the aforementioned airconditioner to have improved refrigeration efficiency and reduced powerconsumption. In order to meet these needs, using HFC refrigerants suchas R410A and R32 that have saturation pressure characteristics that arehigher than those of R22 or R407C has been considered. However, if oneattempts to use a refrigerant such as R410A or R32 as the operatingrefrigerant, not only will the heat source unit and the user units haveto be replaced, but the refrigerant gas junction line and therefrigerant liquid junction line will also have to be replaced withlines that have strengths corresponding to the saturation pressurecharacteristics thereof, and thus the task of installing the airconditioner will be more burdensome than before.

An example of an air conditioner that is capable of solving these typesof problems is the air conditioner disclosed in Japanese PublishedPatent Application No. 2002-106984. This air conditioner has arefrigeration circuit that includes a compressor, a heat source sideheat exchanger, and user side heat exchangers, and a heat source sideauxiliary heat exchanger that is connected in parallel to the heatsource side heat exchanger. When the refrigerant pressure on thedischarge side of the compressor of the air conditioner increases duringcooling operations, the refrigerant on the discharge side of thecompressor is introduced into the heat source side auxiliary heatexchanger and condensed, and thus the refrigerant pressure of therefrigerant circuit between the discharge side of the compressor and theuser side heat exchangers (including the refrigerant liquid junctionline) can be decreased. This allows the heat source unit and the userunits to be replaced with those that use R410A as the operatingrefrigerant, and allows the refrigerant liquid junction line of thepreexisting air conditioner that employs R22 and the like to be left inplace and reused.

However, when pressure is increased in the aforementioned airconditioner, the condensing ability of the refrigerant will temporarilyincrease and an increase in the discharge pressure of the compressorwill be suppressed by operating the heat source side auxiliary heatexchanger, and thus when the condensation temperature of the refrigerantin the heat source side heat exchanger or the heat source side auxiliaryheat exchanger cannot be sufficiently reduced, the pressure of therefrigerant that flows from the heat source side heat exchanger to theuser side heat exchangers (including the refrigerant liquid junctionline) can be reduced to the maximum allowable operating pressure of therefrigerant liquid junction line or lower, but there will be times whenthe refrigerant can only condense to the saturated state or thegas-liquid state. Because of this, the cooling ability of each user unitmay decline.

In addition, as noted above, not only will there be situations in whichthe preexisting refrigerant gas junction line and the refrigerant liquidjunction line of an air conditioner that used R22, R407C, and the likewill be left in place and reused and a new heat source unit and userunits that use the refrigerant such as R410A, R32 as the operatingrefrigerant, and the like having saturation pressure characteristicsthat are higher than those of R22 and R407C will be used with thepreexisting lines, but there will also be situations in whichrefrigerant gas junction lines and the refrigerant liquid junction linesthat have high saturation pressure characteristics such as R410A, R32,and the like cannot be prepared, even when a new air conditioner is tobe installed. In these situations as well, it will be necessary toprotect against a decline in cooling ability in each user unit when therefrigerant condensed in the heat source side heat exchanger is reducedin pressure and sent to the user side heat exchangers.

DISCLOSURE OF THE INVENTION

An object of the present invention is to prevent a decline inrefrigeration ability in a user side heat exchanger when the refrigerantcondensed by a heat source side heat exchanger is reduced in pressureand sent to the user side heat exchanger in a refrigeration equipmentthat includes a vapor compression type of refrigerant circuit.

According to a first aspect of the present invention, the refrigerationequipment includes a heat source unit having a compressor and a heatsource side heat exchanger connected to user units having user side heatexchangers via a refrigerant junction line having a maximum allowableoperating pressure that is lower than that of components that form theheat source unit, and forms a vapor compression type of primaryrefrigerant circuit. The refrigeration equipment further includes afirst expansion mechanism and a cooler. The first expansion mechanismserves to reduce the pressure of a refrigerant that is condensed in theheat source side heat exchanger and sent to the user side heatexchangers down to a pressure that is lower than the allowable operatingpressure of the refrigerant junction line. The cooler serves to cool therefrigerant that is condensed in the heat source side heat exchanger andsent to the user side heat exchangers.

In this refrigeration equipment, the refrigerant that is condensed inthe heat source side heat exchanger can be reduced in pressure by thefirst expansion mechanism and cooled by the cooler, and can then be sentto the user side heat exchangers. Because of this, the refrigerant thatis sent to the user side heat exchangers can be reduced down to apressure that is lower than the maximum allowable operating pressure ofthe refrigerant junction line, and can be maintained in a sub-cooledstate. Thus, a decline in the refrigeration ability in the user sideheat exchangers can be prevented when the refrigerant condensed by theheat source side heat exchanger is reduced in pressure and sent to theuser side heat exchangers.

According to a second aspect of the present invention, the refrigerationequipment of the first aspect of the present invention further comprisesa pressure detection mechanism that serves to detect the pressure of therefrigerant after the pressure thereof has been reduced by the firstexpansion mechanism.

In this refrigeration equipment, the pressure of the refrigerant afterit has been reduced in pressure by the first expansion mechanism can bedetected by means of the pressure detection mechanism, and thus thepressure of the refrigerant between the first expansion mechanism andthe user side heat exchangers can be adjusted to a predeterminedpressure value. Thus, when the refrigerant condensed in the heat sourceside heat exchanger is reduced in pressure and sent to the user sideheat exchangers, the refrigerant pressure can be stably controlled, anda reduction in the refrigeration ability in the user side heatexchangers can be prevented.

According to a third aspect of the present invention, the refrigerationequipment of the second aspect of the present invention, wherein thepressure detection mechanism is a pressure sensor.

In this refrigeration equipment, the refrigerant pressure between thefirst expansion mechanism and the user side heat exchangers can becontinuously monitored while the refrigeration equipment is operating.

According to a fourth aspect of the present invention, the refrigerationequipment of the second aspect of the present invention, wherein thecooler is arranged between the first expansion mechanism and the userside heat exchangers. In addition, the pressure detection mechanism is athermistor arranged between the first expansion mechanism and thecooler.

With this refrigeration equipment, the refrigerant condensed by the heatsource side heat exchanger is reduced in pressure by the first expansionmechanism to form a saturated refrigerant liquid or a two-phaserefrigerant, sent to the cooler and cooled to a sub-cooled state, andthen sent to the user side heat exchangers. Here, the pressure detectionmechanism that includes a thermistor arranged between the firstexpansion mechanism and the cooler measures the temperature of therefrigerant after the pressure thereof has been reduced by the firstexpansion mechanism. The measured refrigerant temperature can beconverted into the saturation pressure of the refrigerant because therefrigerant temperature measured is the temperature of the refrigerantin the saturated state or the gas-liquid state. In other words, thepressure of the refrigerant after pressure reduction by the firstexpansion mechanism can be indirectly measured by means of a pressuredetection mechanism that includes a thermistor. Thus, the refrigerantpressure between the first expansion mechanism and the user side heatexchangers can be stably controlled.

According to a fifth aspect of the present invention, the refrigerationequipment in any of the first to fourth aspects of the presentinvention, wherein the primary refrigerant circuit includes a receiverthat serves to collect the refrigerant condensed in the heat source sideheat exchanger and then send the refrigerant to the first expansionmechanism.

With this refrigeration equipment, refrigerant liquid condensed by theheat source side heat exchanger can be introduced to and temporarilystored in the receiver. Thus, refrigerant liquid that is condensed bythe heat source side heat exchanger is not stored as is in the heatsource side heat exchanger, and the discharge thereof can be expedited.

According the a sixth aspect of the present invention, the refrigerationequipment in any of the first to fifth aspects of the present invetion,wherein the cooler is a heat exchanger that uses the refrigerant whichflows inside the primary refrigerant circuit as a cooling source.

With this refrigeration equipment, the refrigerant that flows inside theprimary refrigerant circuit is used as the cooling source, and thusanother cooling source is unnecessary.

According to a seventh aspect of the present invention, therefrigeration equipment of the sixth aspect of the present invention,wherein the primary refrigerant circuit includes an auxiliaryrefrigerant circuit that serves to reduce the pressure of a portion ofthe refrigerant condensed in the heat source side heat exchanger,introduce the refrigerant to the cooler and exchange heat with therefrigerant that flows in the primary refrigerant circuit side, and thenreturn the heat exchanged refrigerant to the intake side of thecompressor.

With this refrigeration equipment, a portion of refrigerant condensed bythe heat source side heat exchanger is reduced in pressure so that itcan be returned to the intake side of the compressor and used as acooling source for the cooler, and thus a cooling source that has atemperature that is sufficiently lower than the temperature of therefrigerant that flows on the primary refrigerant circuit side of thecooler can be obtained. Thus, the refrigerant that flows on the primaryrefrigerant circuit side can be cooled down to the sub-cooled state.

According to an eighth aspect of the present invention, therefrigeration equipment of the seventh aspect of the present invention,wherein the auxiliary refrigerant circuit includes a second expansionmechanism arranged between the heat source side heat exchanger and thecooler, and a temperature detection mechanism that includes a thermistorarranged on the outlet side of the cooler.

This refrigeration equipment includes a second expansion mechanism and atemperature detection mechanism, and thus the second expansion mechanismcan be adjusted, and the flow rate of the refrigerant that flows in thecooler can be adjusted, based upon the temperature of the refrigerantmeasured by the temperature detection mechanism arranged on the outletof the cooler. Thus, the refrigerant that flows in the primaryrefrigerant circuit can be reliably cooled, and the refrigerant can bereturned to the condenser after it has been evaporated at the outlet ofthe cooler.

According to a ninth aspect of the present invention, the refrigerationequipment in any of the first to eighth aspects of the presentinvention, wherein the refrigerant that flows in the primary refrigerantcircuit and the auxiliary refrigerant circuit has saturation pressurecharacteristics that are higher than those of R407C.

With this refrigeration equipment, the refrigerant liquid that iscondensed by the heat source side heat exchanger can be reduced inpressure by the first expansion mechanism and sent to the user side heatexchangers, and thus even in situations in which maximum allowableoperating pressure of the lines, devices, and the like that form thecircuit between the first expansion mechanism and the user side heatexchangers can only be used up to the saturation pressure of R407C at astandard temperature, a refrigerant that has saturation pressurecharacteristics that are higher than R407C can be used as the operatingrefrigerant. Thus, for example, with a preexisting refrigerationequipment that used R22 or R407C as the operating refrigerant, therefrigerant liquid junction line between the heat source side heatexchanger and the user side heat exchangers of the preexisting devicecan be reused even in situations in which a newly constructedrefrigeration equipment uses a refrigerant having saturation pressurecharacteristics that are higher than those of R407C as the operatingrefrigerant.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a refrigerant circuit of an airconditioner used as an example of the refrigeration equipment of thepresent invention.

FIG. 2 is a Mollier diagram of a refrigeration cycle of an airconditioner during cooling operations.

FIG. 3 is a Mollier diagram of a refrigeration cycle of an airconditioner during heating operations.

FIG. 4 is a schematic diagram of a first modification of the refrigerantcircuit of the air conditioner of the present invention.

FIG. 5 is a schematic diagram of a second modification of therefrigerant circuit of the air conditioner of the present invention.

BEST MODE OF WORKING THE INVENTION

An air conditioner will be described below as an example of therefrigeration equipment of the present invention with reference to thefigures.

(1) Overall Configuration of the Air Conditioner

FIG. 1 is a schematic diagram of a refrigerant circuit of an airconditioner 1 used as an example of the refrigeration equipment of thepresent invention. The air conditioner 1 is a device used, for example,to air condition and heat a building and the like, and includes one heatsource unit 2, a plurality (2 in the present embodiment) of user units 5connected in parallel thereto, and a refrigerant liquid junction line 6and a refrigerant gas junction line 7 that connect the heat source unit2 and the user units 5.

In the present embodiment, the air conditioner 1 uses R410A as anoperating refrigerant, R410A having saturation pressure characteristicsthat are higher than those of R22, R407, and the like. Note that thetype of operating refrigerant is not limited to R410A, and may be R32 orthe like. In addition, in the present embodiment, the air conditioner 1is configured to reuse preexisting heat source units and user units thatused R22, R407, and the like as the heat source unit 2 and the userunits 5. In other words, the refrigerant liquid junction line 6 and therefrigerant gas junction line 7 are the preexisting refrigerant liquidjunction line and the refrigerant gas junction line, and can onlyoperate at the saturation pressure characteristics of R22, R407C, or thelike or lower. Because of this, it will be necessary to operate at themaximum allowable operating pressure or lower of the refrigerant liquidjunction line 6 and the refrigerant gas junction line 7 in situations inwhich an operating refrigerant having saturation pressurecharacteristics that are higher than R410A, R32, or the like are used.More specifically, the refrigerant liquid junction line 6 and therefrigerant gas junction line 7 must be used in a range that does notexceed an operating pressure of approximately 3 MPa, which correspondsto the saturation pressure of R22 and R407C at a normal temperature.Note that the devices and lines that form the heat source unit 2 and theuser units 5 are designed such that they can be used at the saturationpressure (approximately 4 MPa) of R410A at a normal temperature.

(2) Configuration of the User Units

The user units 5 primarily include a user side expansion valve 51, userside heat exchangers 52, and a line that connects these. In the presentembodiment, the user side expansion valve 51 is an electric expansionvalve that is connected to the liquid side of the user side heatexchangers 52, and serves to adjust the refrigerant pressure,refrigerant flow rate and the like. In the present embodiment, the userside heat exchangers 52 are cross fin tube type heat exchangers, andserve to exchange heat with indoor air. In the present embodiment, theuser units 5 take in indoor air into the interior thereof, includes afan for blowing (not shown in the figures), and is capable of exchangingheat between the indoor air and the refrigerant that flows in the userside heat exchangers 52.

(3) Configuration of the Heat Source Units

The heat source unit 2 is primarily composed of a compressor 21, an oilseparator 22, a four way switching valve 23, a heat source side heatexchanger 24, a bridge circuit 25, a receiver 26, a heat source sideexpansion valve 27, a cooler 28, a first auxiliary refrigerant circuit29, a liquid side gate valve 30, a gas side gate valve 41, a secondauxiliary refrigerant circuit 42, and lines that connect these together.

In the present embodiment, the compressor 21 is an electric motor drivenscroll type compressor, and serves to compress the refrigerant gas thathas been drawn therein.

The oil separator 22 is arranged on the discharge side of the compressor21, and is a vessel that serves to separate gas and liquid from oil thatincluded in the refrigerant gas that has been compressed/discharged. Theoil separated in the oil separator 22 is returned to the intake side ofthe compressor 21 via an oil return line 43.

When switching between cooling operations and heating operations, thefour way switching valve 23 serves to switch the direction of therefrigerant flow. During cooling operations, the four way switchingvalve 23 is capable of connecting the outlet of the oil separator 22 andthe gas side of the heat source side heat exchanger 24, and connects theintake side of the compressor 21 and the refrigerant gas junction line 7(refer to the solid line of the four way switching valve in FIG. 1).During heating operations, the four way switching valve 23 connects theoutlet of the oil separator 22 and the refrigerant gas junction line 7,and connects the intake side of the compressor 21 and the gas side ofthe heat source side heat exchanger 24 (refer to the broken line of thefour way switching valve in FIG. 1).

In the present embodiment, the heat source side heat exchanger 24 is across fin tube type of heat exchanger, and serves to exchange heatbetween air and the refrigerant that acts as a heat source. In thepresent embodiment, the heat source unit 2 takes in outdoor air into theinterior thereof, includes a fan for blowing (not shown in the figures),and is capable of exchanging heat between the outdoor air and therefrigerant that flows in the heat source side heat exchanger 24.

The receiver 26 is a vessel that serves to temporarily collect therefrigerant that flows between the heat source side heat exchanger 24and the user side heat exchangers 52. The receiver 26 includes an inletport on the upper portion of the vessel, and a outlet port on the lowerportion of the vessel. The inlet and outlet of the receiver 26 arerespectively connected to the refrigerant circuit between the heatsource side heat exchanger 24 and the cooler 28 via the bridge circuit25. In addition, the heat source side expansion valve 27 is connectedbetween the outlet of the receiver 26 and the bridge circuit 25. In thepresent embodiment, the heat source side expansion valve 27 is anelectric expansion valve that serves to adjust the refrigerant pressureand the refrigerant flow rate between the heat source side heatexchanger 24 and the user side heat exchangers 52.

The bridge circuit 25 is a circuit that is formed from four check valves25 a–25 d that are connected between the heat source side heat exchanger24 and the cooler 28, and includes a function that makes refrigerantflow from the inlet side of the receiver 26 into the receiver 26, andreturns the refrigerant liquid to the refrigerant circuit between theheat source side heat exchanger 24 and the user side heat exchangers 52from the outlet of the receiver 26, even when the refrigerant that flowsin the refrigerant circuit between the heat source side heat exchanger24 and the user side heat exchangers 52 flows either into the receiver26 from the heat source side heat exchanger 24 side, or flows from theuser side heat exchangers 52 side to the receiver 26. More specifically,the check valve 25 a is connected such that the refrigerant that flowsin the direction from the user side heat exchangers 52 side to the heatsource side heat exchanger 24 is guided to the inlet port of thereceiver 26. The check valve 25 b is connected such that the refrigerantthat flows in the direction from the heat source side heat exchanger 24side to the user source side heat exchanger 52 is guided to the inletport of the receiver 26. The check valve 25 c is connected such that therefrigerant that flows from the outlet of the receiver 26 through theheat source side expansion valve 27 can return to the user side heatexchangers 52 side. The check valve 25 d is connected such that therefrigerant that flows from the outlet of the receiver 26 through theheat source side expansion valve 27 can return to the heat source sideheat exchanger 24 side. In this way, the refrigerant that flows into thereceiver 26 from the refrigerant circuit between the heat source sideheat exchanger 24 and the user side heat exchangers 52 will always flowtherein from the inlet of the receiver 26, and the refrigerant from theoutlet of the receiver 26 is returned to the refrigerant circuit betweenthe heat source side heat exchanger 24 and the user side heat exchangers52.

The cooler 28 is a heat exchanger that serves to cool the refrigerantthat is condensed in the heat source side heat exchanger 24 and sent tothe user side heat exchangers 52. In addition, a first pressuredetection mechanism 31 that serves to detect the refrigerant pressure(refrigerant pressure after pressure reduction) between the user sideheat exchangers 52 and the heat source side expansion valve 27 isarranged on the user side heat exchanger 52 side (outlet side) of thecooler 28. In the present embodiment, the first pressure detectionmechanism 31 is a pressure sensor. The aperture of the heat source sideexpansion valve 27 is adjusted so that the refrigerant pressure valuemeasured by the first pressure detection mechanism 31 equals apredetermined pressure value.

The liquid side gate valve 30 and the gas side gate valve 41 arerespectively connected to the refrigerant liquid junction line 6 and therefrigerant gas junction line 7. The refrigerant liquid junction line 6connects the liquid side of the user side heat exchangers 52 of the userunits 5 and the liquid side of the heat source side heat exchanger 24 ofthe heat source unit 2. The refrigerant gas junction line 7 connects thegas side of the user side heat exchangers 52 of the user units 5 and thefour way switching valve 23 of the heat source unit 2. Here, asdescribed above, the primary refrigerant circuit 10 of the airconditioner 1 is connected to the user side expansion valve 51, the userside heat exchangers 52, the compressor 21, the oil separator 22, thefour way switching valve 23, the heat source side heat exchanger 24, thebridge circuit 25, the receiver 26, the heat source side expansion valve27, the cooler 28, the liquid side gate valve 30, and the gas side gatevalve 41 in this order.

Next, the first auxiliary refrigerant circuit 29 and the secondauxiliary refrigerant circuit 42 arranged in the heat source unit 2 willbe described below.

The first auxiliary refrigerant circuit 29 is a refrigerant circuit thatserves to reduce the pressure on a portion of the refrigerant from theoutlet of the receiver 26, introduce the refrigerant to the cooler 28,cause heat to be exchanged with the refrigerant that flows toward theuser side heat exchangers 52, and then return the heat exchanged therefrigerant to the intake side of the compressor 21. More specifically,the first auxiliary refrigerant circuit 29 includes a first branchingcircuit 29 a that is branched from the circuit that connects the outletof the receiver 26 and the heat source side expansion valve 27 andextends toward the cooler 28, an auxiliary side expansion valve 29 bthat is arranged on the first branching circuit 29 a, a first junctioncircuit 29 c that joins the outlet of the cooler 28 with the intake sideof the compressor 21, and a first temperature detection mechanism 29 dthat is arranged on the first junction circuit 29 c.

The auxiliary side expansion valve 29 b is an electric expansion valvethat serves to adjust the flow rate of the refrigerant that flows to thecooler 28. The first temperature detection mechanism 29 d is athermistor that is provided in order to measure the temperature of therefrigerant from the outlet of the cooler 28. Then, the aperture of theauxiliary side expansion valve 29 b is adjusted based upon thetemperature of the refrigerant that is measured by the first temperaturedetection mechanism 29 d. More specifically, the aperture is adjusted bymeans of superheating control between the first temperature detectionmechanism 29 d and the refrigerant temperature of the heat source sideheat exchanger 24. In this way, the refrigerant from the outlet of thecooler 28 can completely evaporate and return to the intake side of thecompressor 21.

The second auxiliary refrigerant circuit 42 is arranged between the fourway switching valve 23 of the primary refrigerant circuit 10 and theuser side heat exchangers 52, and is a refrigerant circuit that iscapable of condensing a portion of the refrigerant that is compressed inthe compressor 21 and sent to the user side heat exchangers 52, and thenreturning that refrigerant to the main refrigerant circuit 10. Thesecond auxiliary refrigerant circuit 42 primarily includes a secondbranching circuit 42 a that serves to branch from the primaryrefrigerant circuit 10 a portion of the refrigerant that is compressedin the compressor 21 and sent to the user side heat exchangers 52, acondenser 42 b that is capable of condensing the branched refrigerant,and a second junction circuit 42 c that is capable of returning thebranched refrigerant to the primary refrigerant circuit 10. In thepresent embodiment, the condenser 42 b is a heat exchanger thatexchanges heat between air that serves as the heat source and therefrigerant.

In addition, a condenser open/close valve 42 d is arranged on the secondjunction circuit 42 c side of the condenser 42 b, and serves topropagate the flow of the refrigerant to the condenser 42 b and to cutthe flow of the refrigerant thereto. The condenser open/close valve 42 dis an electric expansion valve that is capable of adjusting the flowrate of the refrigerant that flows into the condenser 42 b.

In addition, a second pressure detection mechanism 42 e is arranged onthe second junction circuit 42 c, and serves to detect the pressure ofthe refrigerant on the second junction circuit 42 c side (outlet side)of the condenser 42 b. In the present embodiment, the second pressuredetection mechanism 42 e is a pressure sensor. The aperture of thecondenser open/close valve 42 d is adjusted so that the refrigerantpressure value measured by the second pressure detection mechanism 42 eis equal to or less than a predetermined pressure value.

Furthermore, the second auxiliary refrigerant circuit 42 furtherincludes a bypass circuit 42 f that is capable of bypassing thecondenser 42 b and allowing the refrigerant to flow from the compressor21 toward the user side heat exchangers 52. Then, a check mechanism 44that only permits flow from the user side heat exchangers 52 to thecondenser 21 is provided between the connector that connects the secondbranching circuit 42 a to the main refrigerant circuit 10 and theconnector that connects the second junction circuit 42 c to the mainrefrigerant circuit 10. In the present embodiment, the check mechanism44 is a check valve. A capillary tube 42 g that corresponds to apressure drop in the condenser open/close valve 42 d and the condenser42 b is arranged in the bypass circuit 42 f so that the flow rate of therefrigerant that flows into the condenser 42 b can be maintained byadjusting the aperture of the condenser open/close valve 42 d.

(4) Operation of the Air Conditioner

Next, the operation of the air conditioner 1 will be described withreference to FIGS. 1–3. Here, FIG. 2 is a Mollier diagram of arefrigeration cycle when the air conditioner 1 performs coolingoperations, and FIG. 3 is a Mollier diagram of a refrigeration cyclewhen the air conditioner 1 performs heating operations.

{circle around (1)} Cooling Operations

First, cooling operations will be described. During cooling operations,the four way switching valve 23 is in the state shown by the solid linesin FIG. 1, i.e., the discharge side of the compressor 21 is connected tothe gas side of the heat source side heat exchanger 24, and the intakeside of the compressor 21 is connected to the gas side of the user sideheat exchangers 52. In addition, the liquid side gate valve 30 and thegas side gate valve 41 are opened, and the aperture of the user sideexpansion valve 51 is adjusted such that the refrigerant pressure isreduced. The aperture of the heat source side expansion valve 27 isadjusted in order to control the refrigerant pressure in the firstpressure detection mechanism 31 at a predetermined pressure value. Theaperture of the auxiliary side expansion valve 29 b is adjusted bysuperheating control between the first temperature detection mechanism29 d and the refrigerant temperature of the heat source side heatexchanger 24. Here, the condenser open/close valve 42 d of the secondauxiliary refrigerant circuit 42 is closed. In this way, the refrigerantthat flows from the user side heat exchangers 52 to the compressor 21will primarily flow through the check mechanism 44.

When a fan (not shown in the figures) in the heat source unit 2, a fan(not shown in the figures) in the user side units 5, and the compressor21 are started with the primary refrigerant circuit 10 and the auxiliaryrefrigerant circuits 29, 42 in this state, refrigerant gas is taken inby the compressor 21 and compressed from a pressure P_(s1) to a pressureP_(d1), and then the mixture of oil and the refrigerant gas are sent tothe oil separator 22 and the oil is separated therefrom (refer to pointsA₁, B₁ in FIG. 2). After that, the compressed refrigerant gas is sent tothe heat source side heat exchanger 24 via the four way switching valve23, exchanges heat with outdoor air, and is condensed (refer to thepoint C₁ in FIG. 2). The condensed refrigerant liquid flows into thereceiver 26 via the check valve 25 b of the bridge circuit 25. Then,after the refrigerant liquid is temporarily collected in the receiver26, the pressure P_(d1) that is higher than a maximum allowableoperating pressure P_(a1) of the refrigerant liquid junction line 6 isreduced to a pressure P_(e1) that is lower than the pressure P_(a1) inthe heat source side expansion valve 27 (refer to the point D₁ in FIG.2). When this occurs, the reduced pressure refrigerant is in thegas-liquid phase. The reduced pressure refrigerant exchanges heat in thecooler 28 with the refrigerant that flows on the first auxiliaryrefrigerant circuit 29 side thereof and is cooled in order to obtain asub-cooled liquid (refer to the point E₁ in FIG. 2), which is then sentto the user units 5 via the liquid side gate valve 30 and therefrigerant liquid junction line 6. Then, the refrigerant liquid that issent to the user units 5 is reduced in pressure by the user sideexpansion valve 51 (refer to the point F₁ in FIG. 2), and then exchangesheat with indoor air in the user side heat exchangers 52 and evaporated(refer to the point A₁ in FIG. 2). The evaporated refrigerant gas isagain taken into the compressor 21 via the refrigerant gas junction line7, the gas side gate valve 41, the check mechanism 44, and the four wayswitching valve 23. Here, the pressure measured by the first pressuredetection mechanism 31 is controlled to a predetermined pressure value(i.e., pressure P_(e1)) by adjusting the aperture of the heat sourceside expansion valve 27. In addition, a portion of the refrigerantliquid that was collected in the receiver 26 is reduced in pressure to apoint close to the pressure P_(s1) by means of the auxiliary sideexpansion valve 29 b arranged in the first branching circuit 29 a of thefirst auxiliary refrigerant circuit 29, is then introduced into thecooler 28, and then exchanges heat with the refrigerant that flows onthe primary refrigerant circuit 10 side thereof and is evaporated. Then,the evaporated refrigerant is returned to the intake side of thecompressor 21 via the first junction circuit 29 c. In this way, coolingoperations will be carried out in which the refrigerant pressure will bereduced to the pressure P_(e1) that is lower than the maximum allowableoperating pressure P_(a1) of the refrigerant liquid junction line 6, andthe refrigerant liquid will be placed in a sufficiently sub-cooled stateand supplied to the user side heat exchangers 52.

{circle around (2)} Heating Operations

Next, heating operations will be described. During heating operations,the four way switching valve 23 is in the state shown by the brokenlines in FIG. 1, i.e., the discharge side of the compressor 21 isconnected to the gas side of the user side heat exchangers 52, and theintake side of the compressor 21 is connected to the gas side of theheat source side heat exchanger 24. In addition, the liquid side gatevalve 30 and the gas side gate valve 41 are opened, and the apertures ofthe user side expansion valve 51 and the heat source side expansionvalve 25 is adjusted such that the refrigerant pressure is reduced.Here, the auxiliary side expansion valve 29 b is closed, and the firstauxiliary refrigerant circuit is not used. The aperture of the condenseropen/close valve 42 d of the second auxiliary refrigerant valve 42 isadjusted in order to control the refrigerant pressure in the secondpressure detection mechanism 42 e to a predetermined pressure value.

When a fan (not shown in the figures) in the heat source unit 2, a fan(not shown in the figures) in the user side units 5, and the compressor21 are started with the primary refrigerant circuit 10 and the auxiliaryrefrigerant circuits 29, 42 in this state, refrigerant gas is taken inby the compressor 21 and compressed from a pressure P_(s2) to a pressureP_(d2), and then the mixture of oil and the refrigerant gas are sent tothe oil separator 22 and the oil is separated therefrom (refer to pointsA₂, B₂ in FIG. 3). After that, the compressed refrigerant gas is sent tothe user units 5 via the four way switching valve 23. Here, the flow ofthe refrigerant gas is cut by means of the check mechanism 44 arrangedbetween the four way switching valve 23 and the gas side gate valve 41,and the refrigerant gas flows to the user units 5 side via the secondauxiliary refrigerant circuit 42.

After the refrigerant gas flows into the second branching circuit 42 a,it is branched into a flow that returns to the second junction circuit42 c via the bypass circuit 42 f of the second auxiliary refrigerantcircuit 42 and a flow that returns to the junction circuit 42 c via thecondenser 42 b and the condenser open/close valve 42 d. The refrigerantgas that flows in the bypass circuit 42 f is reduced in pressuresomewhat by the capillary 42 g and returns to the second junctioncircuit 42 c (refer to point C₂ in FIG. 3). On the other hand, the flowrate of the refrigerant gas that flows into the condenser 42 b isdetermined in accordance with the aperture of the condenser open/closevalve 42 d, the refrigerant gas exchanges heat with outdoor air and iscondensed to refrigerant liquid, and then returns to the second junctioncircuit 42 c (refer to point H₂, I₂ of FIG. 3). The mixed refrigerantgas that returns to the second junction circuit 42 c is reduced inpressure from a pressure P_(d2) of the refrigerant gas that flows in thesecond branching circuit 42 a to a pressure P_(e2) that is lower than amaximum allowable operating pressure P_(a2) of the refrigerant gasjunction line 7, by means of a pressure reduction effect caused by thereduction of the volume of the refrigerant gas in response to thecondensation of the refrigerant gas in the condenser 42 b, and is thenreturned to the main refrigerant circuit 10 and sent to the user sideheat exchangers 52 (refer to the point D₂ in FIG. 3). Here, the apertureof the condenser open/close valve 42 d is adjusted so that therefrigerant pressure measured by the second pressure detection mechanism42 e arranged in the second junction circuit 42 c equals the pressureP_(e2), and the amount of condensation of the refrigerant gas in thecondenser 42 b is controlled, i.e., the pressure of the refrigerant gassent to the user side heat source unit 52 is controlled. In addition,the state of the refrigerant gas after it has been reduced in pressureby pressure reduction control (point D₂ in FIG. 3) is near the lineindicating the degree of compression caused by the compression 21 (theline connecting point A₂ and point B₂ in FIG. 3). This indicates that arefrigerant temperature can be obtained by pressure reduction controlthat is approximately the same as the temperature of the refrigerantwhen the refrigerant gas is compressed up to pressure P_(e2) by thecompressor 21. In this way, the refrigerant gas that is sent to the userside heat exchangers 52 is sent at a refrigerant temperature that is thesame as that when the refrigerant gas is compressed up to pressureP_(e2) by means of the compressor 21.

As noted above, after gas that is to be sent to the user side heatexchangers 52 is reduced in pressure down to pressure P_(e2), it isreturned to the main refrigerant circuit 10 and sent to the user units 5via the gas side gate valve 41 and the refrigerant gas junction line 7.Then, the refrigerant gas sent to the user unit 5 exchanges heat withindoor air by means of the user side heat exchangers 52 and is condensed(refer to the point E₂ in FIG. 3). After the condensed refrigerantliquid is reduced in pressure down to a pressure P_(f2) in the user sideexpansion valve 51 (refer to the point F₂ of FIG. 3), it is sent to theheat source unit 2 via the refrigerant liquid junction line 6. Then, therefrigerant liquid that is sent to the heat source unit 2 is reduced inpressure down to pressure P_(s2) by the heat source side expansion valve25 (refer to point G₂ in FIG. 3), and then exchanges heat with outdoorair in the heat source side heat exchanger 24 and evaporated (refer tothe point A₂ in FIG. 3). The evaporated refrigerant gas is again takeninto the compressor 21 via the four way switching valve 23. In this way,heating operations are carried out in which the refrigerant pressure isreduced to a pressure P_(e2) that is lower than the maximum allowableoperating pressure P_(a2) of the refrigerant gas junction line 7, andthe refrigerant gas is adjusted to a refrigerant temperature that is thesame as that obtained when the refrigerant gas is compressed by thecompressor 21 and then provided to the user side heat exchangers 52.

(5) Special Characteristics of the Air Conditioner of the PresentEmbodiment

As described below, the special characteristics of the air conditioner 1of the present embodiment are as follows:

{circle around (1)} Special Characteristics During Cooling Operations

In the air conditioner 1 of the present embodiment, after therefrigerant condensed in the heat source side heat exchanger 24 isreduced in pressure by the heat source side expansion valve 27 andcooled by the cooler 28, it can be sent to the user side heat exchangers52. Because of this, the refrigerant to be sent to the user side heatexchangers 52 can be reduced in pressure and can be kept in thesub-cooled state. In addition, the pressure of the refrigerant can beadjusted to a predetermined pressure value (pressure P_(e1) in FIG. 2)between the heat source side expansion valve 27 and the user side heatexchangers 52, because the pressure of the refrigerant can be detectedby means of the first pressure detection mechanism 31 after it has beenreduced in pressure in the heat source side heat exchanger 27. Thus,when the refrigerant condensed in the heat source side heat exchanger 24is reduced in pressure and sent to the user side heat exchangers 52, therefrigerant pressure can be stably controlled, and a reduction in thecooling ability of the user side heat exchangers 52 can be prevented. Inthe present embodiment, as shown in FIG. 2, the change in enthalpyh_(E1) after the reduction in pressure in the heat source side expansionvalve 27 is larger than the change in enthalpy h_(D1) before thereduction in pressure therein, and thus the cooling ability perrefrigerant flow rate unit will increase.

In addition, in the air conditioner 1, the first pressure detectionmechanism 31 is a pressure sensor, and thus during cooling operations,the refrigerant pressure between the heat source side expansion valve 27and the user side heat exchangers 52 can be continuously monitored, andthe reliability of the refrigerant pressure will be high.

Furthermore, with the air conditioner 1, the pressure of the refrigerantliquid condensed by the heat source heat exchanger 24 can be reduceddown to a pressure P_(e1) that is lower than the maximum allowableoperating pressure P_(a1) of the refrigerant liquid junction line 6 bymeans of the heat source side expansion valve 27 and sent to the userside heat exchangers 52, and thus as in the present embodiment, arefrigerant having saturation pressure characteristics that are higherthan those of R407C can be used as the operating refrigerant, even insituations in which the maximum allowable operating pressure of thelines and devices that form the circuit between the heat source sideexpansion valve 27 and the user side heat exchangers 52 only extends upto the saturation pressure of R407C at a standard temperature. Thus, inthe present embodiment, the refrigerant liquid junction line 6 of apreexisting air conditioner that used R22 or R407C as the operatingrefrigerant can be reused, even in situations in which the newlyconstructed air conditioner 1 uses a refrigerant having saturationpressure characteristics that are higher than those of R407C as theoperating refrigerant.

In addition, the air conditioner 1 includes a receiver 26 that serves tocollect the refrigerant condensed in the heat source side heat exchanger24 and send the refrigerant to the heat source side expansion valve 27,and thus the refrigerant liquid condensed by the heat source side heatexchanger 24 is not stored inside the heat source side heat exchanger 24as is, and the discharge therefrom can be facilitated. Thus, pooling ofthe refrigerant liquid can be reduced in the heat source side heatexchanger 24, and heat exchange can be facilitated.

Furthermore, with the air conditioner 1, refrigerant liquid can be sentto the user side heat exchangers 52 in the sub-cooled state, and thus asin the present embodiment, the refrigerant can be kept in the liquidstate and it will be difficult to produce an unbalanced refrigerantflow, even in situations in which the refrigerant is branched to aplurality of user units 5 or there is a difference in elevation from theheat source unit 2 to the user units 5.

In addition, with the air conditioner 1, the cooler 28 is a heatexchanger that serves as a cooling source for the refrigerant that flowsinside the primary refrigerant circuit 10, and thus another coolingsource is unnecessary. In the present embodiment, the refrigerant thatis introduced into the cooler 28 by means of the first auxiliaryrefrigerant circuit 29 serves as a cooling source. The first auxiliaryrefrigerant circuit 29 uses a portion of the refrigerant condensed bythe heat source side heat exchanger 24 as a cooling source for thecooler, and reduces the pressure thereof to a point in which therefrigerant can return to the intake side of the compressor 21. Becausethe cooling source can attain a temperature that is sufficiently lowerthan that of the refrigerant that flows in the primary refrigerantcircuit 10 side, the refrigerant that flows in the primary refrigerantcircuit 10 side can be cooled to the sub-cooled state. Furthermore, theaperture of the auxiliary side expansion valve 29 b can be adjustedbased upon the refrigerant temperature measured by the first temperaturedetection mechanism 29 d, and thus the flow rate of the refrigerant thatflows in the cooler 28 can be adjusted, because the first auxiliaryrefrigerant circuit 29 includes the auxiliary side expansion valve 29 band the first temperature detection mechanism 29 d that is arranged atthe outlet of the cooler 28. Thus, the refrigerant that flows in theprimary refrigerant circuit 10 can be reliably cooled, and therefrigerant can be returned to the condenser 21 after it has beenevaporated at the outlet of the cooler 28.

{circle around (2)} Special Characteristics During Heating Operations

During heating operations with the air conditioner 1 of the presentembodiment, a portion of the refrigerant that is compressed in thecompressor 21 and sent to the user side heat exchangers 52 can becondensed by the second auxiliary refrigerant circuit 42 to therebyreduce the pressure of the refrigerant that is sent to the user sideheat exchangers 52. This allows the pressure of the refrigerant that issent to the user side heat exchangers 52 to be stably controlled. In thepresent embodiment, the pressure of the refrigerant can be reliablyreduced with good response because the second auxiliary refrigerantcircuit 42 includes the condenser 42 b, the refrigerant that is sent tothe user side heat exchangers 52 by the condenser 42 b is condensed, andthe pressure thereof is reduced by reducing the volume of therefrigerant gas. In addition, the second auxiliary refrigerant circuit42 can also propagate/cut off the flow of refrigerant to the condenser42 b at the appropriate time because it includes the condenseropen/close valve 42 d that can propagate/cut off the flow of refrigerantto the condenser 42 b. Furthermore, the pressure of the refrigerant thatis sent to the user side heat exchangers 52 can be stably controlledbecause the second pressure detection mechanism 42 e that serves todetect the refrigerant pressure between the condenser 42 b and the userside heat exchangers 52 is arranged in the second junction circuit 42 cof the second auxiliary refrigerant circuit 42.

In addition, when the pressure control is carried out by the secondauxiliary refrigerant circuit 42, the state of the refrigerant gas afterit has been reduced in pressure by pressure reduction control (refer topoint D₂ in FIG. 3) is near the line indicating the degree ofcompression caused by the compression 21 (the line connecting point A₂and point B₂ in FIG. 3). The desired heating load will be easilymaintained by means of this pressure reduction control, because thetemperature of the refrigerant gas sent to the user side heat exchangers52 can be set to a temperature that is the same as that when therefrigerant gas is compressed up to a pressure P_(e2) by the compressor21.

Furthermore, a refrigerant can flow through the second auxiliaryrefrigerant circuit 42 when it is sent from the compressor 21 to theuser side heat exchangers 52, and can flow through the check mechanism44 of the primary refrigerant circuit 10 when it is sent from the userside heat exchangers 52 to the compressor 21, because the airconditioner 1 further includes the bypass circuit 42 f arranged in thesecond auxiliary refrigerant circuit 42 and the check mechanism 44arranged in the primary refrigerant circuit 10. This allows the flowpath of the refrigerant gas to be switched during cooling operations andheating operations.

In addition, as shown in FIG. 3, a refrigerant having saturationpressure characteristics that are higher than those of R407C can be usedas the operating refrigerant in the air conditioner 1, even insituations like the present embodiment in which the maximum allowableoperating pressure of the lines and devices that form the circuitbetween the compressor 21 and the user side heat exchangers 52 onlyextends up to the saturation pressure of R407C at a normal temperature,because the refrigerant gas sent to the user side heat exchangers 52 canbe reduced in pressure down to a pressure P_(e2) that is lower than themaximum allowable operating pressure P_(a2) of the refrigerant gasjunction line 7 by condensing a portion of the refrigerant gas that issent from the compressor 21 to the user side heat exchangers 52 by meansof the second auxiliary refrigerant circuit 42. Thus, in the presentembodiment, the refrigerant gas junction line 7 of a preexisting airconditioner that used R22 or R407C as the operating refrigerant can bereused, even in situations in which the newly constructed airconditioner 1 uses a refrigerant having saturation pressurecharacteristics that are higher than those of R407C as the operatingrefrigerant.

(6) Modification 1

In the aforementioned embodiment, a first pressure detection mechanism31 that includes a pressure sensor is arranged between the cooler 28inside the heat source unit 2 and the liquid side gate valve 30 of theair conditioner 1. However, as shown in FIG. 4, an air conditioner 101may include a heat source unit 102 in which a first pressure detectionmechanism 131 that includes a thermistor is arranged between a bridgecircuit 25 and the cooler 28. Note that a description of the otherstructure of the air conditioner 101 will be omitted because it isidentical with that of the air conditioner 1.

In the air conditioner 101, the refrigerant condensed by the heat sourceside heat exchanger 24 is reduced in pressure by the heat source sideexpansion valve 27 to form a saturated refrigerant liquid or a two-phaserefrigerant, sent to the cooler 28 and cooled to a sub-cooled state, andthen sent to the user side heat exchangers 52. Here, the first pressuredetection mechanism 131 that includes a thermistor and arranged betweenthe heat source side expansion valve 27 and the cooler 28 measures thetemperature of the refrigerant after the pressure thereof has beenreduced by the heat source side expansion valve 27. The measuredrefrigerant temperature is the temperature of refrigerant in thesaturated state or the gas-liquid state, and thus the saturationpressure of the refrigerant can be determined from this temperature. Inother words, the pressure of the refrigerant after pressure reduction inthe heat source side expansion valve 27 can be indirectly measured bymeans of the first pressure detection mechanism 131. Like in theaforementioned embodiment, this allows the refrigerant pressure betweenthe heat source side expansion valve 27 and the user side heatexchangers 52 to be stably controlled.

(7) Modification 2

In the aforementioned embodiment, the second auxiliary refrigerantcircuit 42 inside the heat source unit 2 of the air conditioner 1includes an air cooling type of condenser 42 b. However, as shown inFIG. 5, an air conditioner 201 may include a heat source unit 202 inwhich a second auxiliary refrigerant circuit 242 is arranged, and havinga condenser 242 b that uses the refrigerant flowing in a primaryrefrigerant circuit 210 as a cooling source. Here, the cooling source ofthe condenser 242 b is the refrigerant that is reduced in pressure by anauxiliary side expansion valve 229 b of a first auxiliary refrigerantcircuit 229, and is the same as the cooling source of the cooler 28.

The first auxiliary refrigerant circuit 229 is primarily formed from afirst branching circuit 229 a that is branched from the circuit thatconnects the outlet of the receiver 26 and the heat source sideexpansion valve 27 and extends toward the cooler 28 and the condenser242 b, and a first junction circuit 229 c that joins the outlet of thecooler 28 and the outlet of the condenser 242 b to the intake side ofthe compressor 21. The first branching circuit 229 a includes a primarybranching circuit 229 a, an auxiliary side expansion valve 229 b that isarranged in the primary branching circuit 229 a, a cooler side branchingcircuit 229 c that is arranged on the downstream side of the auxiliaryside expansion valve 229 b and connected to the inlet of a cooler 28,and a condenser side branching circuit 229 e that is arranged on thedownstream side of the auxiliary side expansion valve 229 b andconnected to the inlet of a condenser 242 b. The cooler side branchingcircuit 229 c includes a branching open/close valve 229 d that serves topropagate/cut off the flow of the refrigerant to the cooler 28. Inaddition, the condenser side branching circuit 229 e includes abranching open/close valve 229 f that serves to propagate/cut off theflow of the refrigerant to the condenser 242 b. The first junctioncircuit 229 c includes a primary junction circuit 229 i that joins withthe intake side of the compressor 21, a cooler side junction circuit 229c that joins the outlet of the cooler 28 with the primary junctioncircuit 229 i, a condenser side joining circuit 229 h that joins theoutlet of the condenser 242 b to the primary junction circuit 229 i, anda first temperature detection mechanism 229 j that is arranged in theprimary junction circuit 229 i. Note that a description of the otherstructure of the air conditioner 201 will be omitted because it isidentical with that of the air conditioner 1.

After the branching open/close valve 229 d is opened so that the cooler28 can be used, and the branching open/close valve 229 f is closed sothat the condenser 242 b is not used, the air conditioner 201 canconduct cooling operations like with the air conditioner 1. In addition,after the branching open/close valve 229 d is closed so that the cooler28 is not used, and the branching open/close valve 229 f is opened sothat the condenser 242 b can be used, the air conditioner 201 canconduct heating operations like with the air conditioner 1. In otherwords, pressure control of the primary refrigerant circuit 210 can bestably performed by switching between the branching open/close valve 229d, 229 f in accordance with the operational mode.

(8) Other Embodiments

Although an embodiment of the present invention was described abovebased upon the figures, the specific configuration of the presentinvention is not limited to this embodiment, and can be modified withina range that does not depart from the essence of the invention.

{circle around (1)} Although the heat source units used in the airconditioner in the aforementioned embodiment are the air cooling typewhich use outdoor air as a heat source, water cooling types or icestorage types of heat source units may also be used.

{circle around (2)} In the aforementioned embodiment, a pressure sensoris used in the second pressure detection mechanism, however a pressureswitch may also be used. This allows a faster control response. Inaddition, the condenser open/close valve need not be an electricexpansion valve, but rather a solenoid valve that has no restrictionfunction. Thus, although a smooth control response cannot be obtainedcompared to when an electric expansion valve is used, a prompt controlresponse can be obtained.

{circle around (3)} In the aforementioned embodiment, a capillary tubeis arranged in the bypass circuit, however the diameter of the line thatforms the bypass circuit may simply be reduced so that the pressure dropcan be maintained.

{circle around (4)} In the aforementioned embodiment, an operation wasdescribed in which the discharge pressure of the compressor is alwayshigher than the pressure in the refrigerant liquid junction line and therefrigerant gas junction line. However, a control that is combined withcapacity control by means of inverter control and the like of thecompressor is also possible. For example, possible operations includecontrolling the refrigerant pressure measured by the discharge pressuresensor and the like of the compressor by means of capacity control ofthe compressor such that the pressure thereof is lower than the maximumallowable operating pressure of the refrigerant liquid junction line andthe refrigerant gas junction line, opening the heat source sideexpansion valve and the condenser open/close valve to reduce therefrigerant pressure only when the pressure detected by the first andsecond pressure detection mechanisms approaches the maximum allowableoperating pressure of the refrigerant liquid junction line and therefrigerant gas junction line, and the like.

{circle around (5)} In the aforementioned embodiment, the configurationdescribed is one in which a preexisting heat source unit and user unitsof an air conditioner that used R22 R407C, or the like are replaced withthe heat source unit 2 and the user units 5, and the preexistingrefrigerant liquid junction line and the refrigerant gas junction linethat can only operate at or below the saturation pressures of R22,R407C, and the like are used as is. However, the aforementionedembodiment is not limited thereto. For example, even in situations inwhich a new air conditioner is to be installed, there will be times inwhich a refrigerant gas junction line and a refrigerant liquid junctionline that use a refrigerant having high saturation pressurecharacteristics such as R410A, R32, and the like cannot be prepared, andthus, like in the aforementioned embodiment, it is possible to adapt thepresent invention to these situations. Thus, it will be possible toconstruct an air conditioner that employs a refrigerant gas junctionline and a refrigerant liquid junction line that can be preparedon-site, and which uses a refrigerant having high saturation pressurecharacteristics such as R410A, R32, and the like as the operatingrefrigerant.

INDUSTRIAL APPLICABILITY

According to the present invention, a refrigerant condensed in the heatsource side heat exchanger is reduced in pressure by the first expansionmechanism and cooled by the cooler, and is then sent to the user sideheat exchangers, and thus when the refrigerant condensed by the heatsource side heat exchanger is reduced in pressure and sent to the userside heat exchangers, a decline in the refrigeration abilities of theuser side heat exchangers can be prevented.

1. A refrigeration equipment comprising: a vapor compression type ofprimary refrigerant circuit including a compressor, a heat source sideheat exchanger, a plurality of user side heat exchangers connected tothe heat source side heat exchanger via a refrigerant junction linehaving a maximum allowable operating pressure; a first expansionmechanism configured to reduce a pressure of a refrigerant that iscondensed in the heat source side heat exchanger and sent to the userside heat exchangers down to a pressure that is lower than the maximumallowable operating pressure of the refrigerant junction line; and acooler configured to cool the refrigerant that is condensed in the heatsource side heat exchanger and sent to the user side heat exchangers. 2.The refrigeration equipment disclosed in claim 1, further comprising apressure detection mechanism configured to detect the pressure of therefrigerant after the pressure thereof has been reduced by the firstexpansion mechanism.
 3. The refrigeration equipment disclosed in claim2, wherein the pressure detection mechanism is a pressure sensor.
 4. Therefrigeration equipment disclosed in claim 2, wherein the cooler isarranged between the first expansion mechanism and the user side heatexchangers; and the pressure detection mechanism is arranged between thefirst expansion mechanism and the cooler.
 5. The refrigeration equipmentdisclosed in claim 1, wherein the primary refrigerant circuit comprisesa receiver configured to collect the refrigerant condensed in the heatsource side heat exchanger and then send the refrigerant to the firstexpansion mechanism.
 6. The refrigeration equipment disclosed in claim1, wherein the cooler is a heat exchanger that is configured to use therefrigerant that flows inside the primary refrigerant circuit as acooling source.
 7. The refrigeration equipment disclosed in claim 6,wherein the primary refrigerant circuit comprises an auxiliaryrefrigerant circuit configured to reduce a pressure of a portion of therefrigerant condensed in the heat source side heat exchanger, introducethe refrigerant to the cooler and exchange heat with the refrigerantthat flows in a primary refrigerant circuit side, and then return theheat exchanged refrigerant to an intake side of the compressor.
 8. Therefrigeration equipment disclosed in claim 7, wherein the auxiliaryrefrigerant circuit comprises a second expansion mechanism arrangedbetween the heat source side heat exchanger and the cooler, and atemperature detection mechanism that includes a thermistor arranged onan outlet side of the cooler.
 9. The refrigeration equipment disclosedin claim 7, wherein the refrigerant that flows in the primaryrefrigerant circuit and the auxiliary refrigerant circuit has saturationpressure characteristics that are higher than those of R407C.
 10. Therefrigeration equipment disclosed in claim 8, wherein the refrigerantthat flows in the primary refrigerant circuit and the auxiliaryrefrigerant circuit has saturation pressure characteristics that arehigher than those of R407C.
 11. The refrigeration equipment disclosed inclaim 2, wherein the primary refrigerant circuit comprises a receiverconfigured to collect the refrigerant condensed in the heat source sideheat exchanger and then send the refrigerant to the first expansionmechanism.
 12. The refrigeration equipment disclosed in claim 11,wherein the cooler is a heat exchanger that is configured to use therefrigerant that flows inside the primary refrigerant circuit as acooling source.
 13. The refrigeration equipment disclosed in claim 12,wherein the primary refrigerant circuit comprises an auxiliaryrefrigerant circuit configured to reduce a pressure of a portion of therefrigerant condensed in the heat source side heat exchanger, introducethe refrigerant to the cooler and exchange heat with the refrigerantthat flows in a primary refrigerant circuit side, and then return theheat exchanged refrigerant to an intake side of the compressor.
 14. Therefrigeration equipment disclosed in claim 13, wherein the auxiliaryrefrigerant circuit comprises a second expansion mechanism arrangedbetween the heat source side heat exchanger and the cooler and atemperature detection mechanism that includes a thermistor arranged onan outlet side of the cooler.
 15. The refrigeration equipment disclosedin claim 14, wherein the refrigerant that flows in the primaryrefrigerant circuit and the auxiliary refrigerant circuit has saturationpressure characteristics that are higher than those of R407C.
 16. Therefrigeration equipment disclosed in claim 13, wherein the refrigerantthat flows in the primary refrigerant circuit and the auxiliaryrefrigerant circuit has saturation pressure characteristics that arehigher than those of R407C.
 17. The refrigeration equipment disclosed inclaim 5, wherein the cooler is a heat exchanger that is configured touse the refrigerant that flows inside the primary refrigerant circuit asa cooling source.
 18. The refrigeration equipment disclosed in claim 17,wherein the primary refrigerant circuit comprises an auxiliaryrefrigerant circuit configured to reduce a pressure of a portion of therefrigerant condensed in the heat source side heat exchanger, introducethe refrigerant to the cooler and exchange heat with the refrigerantthat flows in a primary refrigerant circuit side, and then return theheat exchanged refrigerant to an intake side of the compressor.
 19. Therefrigeration equipment disclosed in claim 18, wherein the auxiliaryrefrigerant circuit comprises a second expansion mechanism arrangedbetween the heat source side heat exchanger and the cooler and atemperature detection mechanism that includes a thermistor arranged onan outlet side of the cooler.
 20. The refrigeration equipment disclosedin claim 18, wherein the refrigerant that flows in the primaryrefrigerant circuit and the auxiliary refrigerant circuit has saturationpressure characteristics that are higher than those of R407C.
 21. Arefrigeration equipment comprising: a vapor compression type of primaryrefrigerant circuit including a compressor, a heat source side heatexchanger, a plurality of user side heat exchangers connected to theheat source side heat exchanger via a refrigerant junction line having amaximum allowable operating pressure; a first expansion mechanismconfigured to reduce a pressure of a refrigerant that is condensed inthe heat source side heat exchanger and sent to the user side heatexchangers down to a pressure that is lower than the maximum allowableoperating pressure of the refrigerant junction line; and a coolerconfigured to cool the refrigerant that is condensed in the heat sourceside heat exchanger and sent to the user side heat exchangers, therefrigerant that flows in the primary refrigerant circuit havingsaturation pressure characteristics that are higher than those of R407C.